Leveraging Long‐Life Alkaline Redox Flow Batteries Using Durable and High‐Hydroxide Exchange N‐Bridged Triazine Framework Membranes

Abstract Fluorine‐free organic framework polyelectrolyte membranes showing near frictionless ionic conductivities are gaining cognitive insights. However, the co‐precipitation of COFs in the membranes often brings trade‐offs to commission long‐life electrochemical energy storage solutions. Herein, a durable and ionically miscible dual‐ion exchange membrane based on triazine organic framework (TOF) is designed for alkaline redox flow batteries (RFB). Bearing dual ion‐exchange architectures, the all‐hydrocarbon TOF‐based PEMs ( s TOF's) surpass fluorinated Nafion in terms of energy efficiency (>80%), energy density, and peak power densities. The fabricated s TOF's evidenced the highest net ion‐exchange of >2.1 meq g ⁻¹ which encourages electrolyte utilization with ≈100% and offers excellent capacities. Moreover, >97% efficiencies are preserved, and rate capability studies illustrate that, with s TOF‐5, the RFB can operate at reduced overpotentials (η ≤200 mV) and can uplift batteries life. The s TOF's supports successful demonstrations of batteries at higher redoxolyte concentrations thereby multiplying the energy densities. The afterlife performance of s TOF‐5 revealed efficiencies equivalent to fresh Nafion‐117 and surpassed bearing >50% capacity after ≈3000 continuous cycles. With s TOF‐5, the cell delivered a peak power (P _max ) of 2.3 W which is ≈60% higher than that of Nafion‐117 (P _max = 1.45 W).